The invention relates to a flywheel energy accumulator with a vertical shaft which carries upper and lower flywheels and is supported by at least one passive super conductive magnetic axial thrust bearing. A homopolar electrodynamic machine is provided which has a rotor mechanically coupled to the flywheel, and a stator which is stationary relative to the vacuum housing of the energy accumulator.
Flywheel energy accumulator with conventional bearings have only a relatively small storage potential because of a relatively high bearing friction and the energy consumption caused thereby. With contact-free active magnetic bearings, it is necessary, on one hand, to provide an expensive and complicated electronic sensing and control system, and, on the other hand, the attenuation, which is generally insufficient, must be compensated for by the installation of additional eddy current dampers.
Another disadvantage resides in the rigidity of the bearing which increases with the rotor speed.
Because they do not have these disadvantage superconductive magnetic bearings are particularly suitable for flywheel energy accumulators because they can store electric energy with low losses. Since such bearings require no control system, they are called self-stabilizing or passive bearings. With flywheel energy accumulators electric energy is converted in a motor/generator unit into kinetic energy and is stored in a strong flywheel disc. It is important in this connection that the losses in the storing phase are minimized in order to prevent the discharge that is the loss of the energy. For this reason, the rotor of the system is supported on the superconductive magnets referred to earlier in a contact-free manner. Such a system is known, for example, from Bornemann, H. J. et al., "Schwungradenergiespeicher mit passiven supraleitenden magnetischen Lagern", (Flywheel energy accumulator with passive, superconductive magnetic bearings), KFK-Nachrichten 26 issue March 1994 pages 209-214.
It is the object of the present invention to provide such a flywheel energy accumulator which, on one hand, has minimal energy losses and, on the other hand, has a high energy storage capacity.